Prior art independent-drive wheels are in the form of a combination of a motor from which torque is mechanically transmitted through a reduction gear or a shaft to a wheel.
Also known in the art are independent-drive wheels which do not have a mechanical transmission, e.g., hydraulic independent-drive wheels (SU, A, 1357257) or air-powered independent-drive wheels (SU, A, 1050920).
The most promising are independent-drive wheels in which rotation is imparted to a wheel be means of an electromagnetic gearless cooperation of magnetic systems of a stator and rotor (SU, A, 628008).
Independent-drive wheels may also be used in which a prime mover is in the form of an internal combustion engine. However, the use of this prime mover is not only ineffective in view of the use of a fuel and the need to have auxiliary lubrication and cooling systems, and because of a large size, but also because of undesirable polution of the environment.
Most widespread used are independent-drive wheels having a reduction gear and an induction motor which have high speeds to result in a gain in power. In comparison with internal combustion engines, these independent-drive wheels are ecologically safe, more reliable and economical.
However, the use of a reduction gear brings about an increased risk and hampers operation, and the employment of an induction motor calls for the provision of sophisticated voltage converter units and control units as well as auxiliary lubrication and cooling systems.
In addition, it is not possible to ensure recuperation of energy during movement; storage battery life is short, and high-voltage power supplies have to be used. All this do not allow geared independent-drive wheels powered by an induction motor to be regarded as promising for the future.
Known in the art independent-drive wheels having a d-c motor which transmits torque (SU, A, 375214). The d-c motor has a hollow flexible cylindrical rotor having a ring gear engageable with a gear having its axle which is the wheel axle.
The main disadvantage is the need for a large energy consumption and motor power (especially at starting of a vehicle), large size and heavy weight.
The most similar to the invention is an independent-drive wheel of a wheel-mounted vehicle, comprising a wheel having a rim and a shaft incorporating an induction motor (SU, A, 1628008). The electric motor is in the form of a disk-type induction machine having its stator with a magnetic circuit, windings and current leads secured to a fixed axle of the wheel and a squirrel-cage rotor having a winding and magnetic circuits positioned on either side of the stator to form a wheel which is rotatable with respect to the stator. The rotor carries a rim which is provided with a pneumatic tire or other device.
The motor disks are made of an electrically conducting material, and short-circuit conductors of the rotor winding terminating in end portions of magnetic circuits through which the axial magnetic flux is closed.
Radially extending vanes for intensifying heat removal from the disk surface and increasing load-bearing capacity of the wheel are externally provided on the outer side of the rotor disks.
This construction of the independent-drive wheel ensures an enhanced reliability owing to the absence of a mechanical gear and enhances stator and rotor cooling through radial passages of the stator washed with a coolant and communicating with inlet and outlet pipes provided in the fixed axle and through radial interior spaces of the rotor.
The prior art independent-drive wheel, which makes use of an induction motor, has a low reliability in operation, high heat emission as a result of a residual field in the magnetic system of the electric motor because of counter-emf, and poor controllability because of the absence of a link between dynamics of rotation and control signals.
In addition, the prior art independent-drive wheel has a sophisticated control system, makes use of high-voltage power supplies having a short life in a voltage control unit, and cannot work with energy recuperation during movement and braking of a vehicle.
This independent-drive wheel is not ecologically safe to a sufficient extent; it is difficult in maintenance and inspection, rather unsafe and expensive because of the use of high-voltage power supplies.
In view of the above, the main problem arising in the development of independent-drive wheels for wheel-mounted vehicles such as electric cars, electric forklifts, electric tractors, electric bicycles, wheelchairs, and the like, is the problem of the provision and development of a special electric machine which is to comply with the following basic requirements:
possibility of incorporation in a vehicle wheel without the use of a gear;
use of low-voltage electrical power supplies;
maximum simplicity, low weight and compactness;
enhanced reliability and long service life;
maximum torque at starting of a vehicle and torque reduction with an increase in the wheel speed;
absence of auxiliary cooling and lubrication systems;
optimum thermal conditions;
counter-emp energy recuperation;
facilitated control of independent-drive wheels and possibility of maneuvering within restricted areas.